Method of forming an extension upon tubes



Oct. 22, 1929.

A. T. HUNTER METHOD OFFORMIN-G AN EXTENSION UPON TUBES Original FiledDec. 16, 1926 INVENTOR:

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Patented Oct. 22, 1929 UNITED STATES PATENT; OFFICE ARTHUR T. HUNTER, OFUNIVERSITY CITY, MISSOURI, ASSIGNOR TO INTERNATIONAL COMBUSTIONENGINEERING CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWAREMETHOD OF FORMING AN EXTENSION UPON TUBES Original application filedDecember 16, 1926, Serial No. 155,197. Divided and this applicationfiled September 24, 1928.

This invention is a novel method of an apparatus for forming anextension upon a tube, having reference particularly to the producing ofa heattransferring or integral metallic extension upon a preformedcirculation tube. The present invention, constituting a division of myprior application Serial No. 155,197, filed December 16, 1926, isillustrated as used for the manufacture of wall elements for boilerfurnaces and the like, especially for water Walls adapted to functionfor the generation or superheating of steam or for keeping relativelycool a furnace wall or other exposed surface by preventing overheating'due to high rates and temperatures of combustion.

The general object of the present invention is to afford a method of andapparatus for formin an extension upon a circulation tube which 1spractical, effective and economical and which will produce a product ofhigh efficiency, strength and durability. Other and further objectsandadvantages of the present invention will be elucidated in thehereinafter following description ofone or more embodiments thereof orwill be understood by those skilled in the subject.

In the accompanying drawings Figs. 1 to correspond with Figs. 1, 3, 6, 7and 8 respectively of the parent application of which this is adivision.

Fig. 1 is a transverse section of a circulation tube or wall elementconstituting an illustrative embodiment of the product of the presentinvention.

Fig. 2 is a perspective view showing the preferred longitudinalstructure of the wall element having a cross. section such as Fig. 1.Fig. 3 is a cross section of a manufacturing apparatus by which themethod of the present invention can be carried out for making a wallelement such as shown in Figs. 1 and 2. Fig. 4 is a diagrammatic partialview on an enlar ed scale indicating the operations taking place in theapparatus of Fig. 3.

Fig. 5 is a top plan view of an apparatus such as is shown in Figs. 3and 4, arranged for reducing a wall element having a longitudinalstructure such as indicated in Fig. 2.

The tubular wall element is shown as a Serial No. 307,984.

whole in cross section in Fig. 1 and consists of the tube portion 11containing the water passage 12 and the exterior extension or facing 13.By water it is intended to include water either in liquid form or vapor,or other circulating fluid. The particular form of extension or facing13 may be described as comprising a body 14 and opposite wings 15rendering the facing substantially wider than the diameter of the tube,and the fi ont face or surface 16 extending over the whole width of thebody and wings.

As will be described the metal constituting the extension 13 is integralwith the circulationtube 11, but as the tube consists preferably ofdifferent metals the drawing indicates a theoretical division, or lineof union 17 between them. The complete element 10 is composed of thepreformed tube 11 preferably of steel, with an integrally united or fusewelded extension 13, of ferrous metal, preferably of cast iron. The tubemay be a seamless wrought steel tube of standard type as used for boilertubes, while the extension consists preferably of gray cast ironcastdirectly and integrally upon the tube as will be described.

The purpose of the particular cross section form of the extension orfacing and the heat transferring operation thereof as a part of afurnace or water wall are fully described in said parent application towhich reference is hereby made. The desired results of transfer orconduction of heat would not be attainable under practical conditionsunless the tube portion and extension are unitarily connected, and theline or union 17 therefore in dicates a line of intimate or absolutecontact between the twoportions, with molecules or crystals interlockedcontinuously along the contiguous portions of the original tube and theapplied extension.

The extension facin is preferably formed in relatively short sections asshown at 13, 13 in Fig. 2 instead of continuously for the length of thetube. This leaves spaces 23 between sections which facilitatemanufacture arrangement also allows for the gradual growth which occurswith repeated beatings of ferrous metals. While a mild steel, low incarbon, is preferablefor the preformed tube, cast ironis superior forthe facing, for example a gray cast iron high in carbon, and the rapidtransfer of heat enables the iron to be kept from excessivetemperatures. Takinga specific instance, I may use a #9 seamless boilertube 11, having a diameter of about 3 inches, with spaces between thesections of 4 inch, and each section about 6 inches long and a widthslightly less than the spacing between the tubes, so as to leave spacesin all directions.

The .water wall element, hereinabove described, may be manufactured onan economical basis by the following method. Starting With a standardseamless steel tube 11 of the desired shape and length this should firstbe thoroughly cleaned prior to the casting operations. It should firstbe dipped in pickling acid to loosen the scale, for at least half of thecircumference of the tube, and this should be followed by sand blastinguntil the surface is bright and clean.

A portion of the length of the tube may then be inserted in a specialmold such as is indicated in Fig. 3. This comprises a lower mold section32 and above it a removable upper section or cope 33. The casting space34 corresponds with the cross section shape of the facing extension 13as seen in Fig. 1, and is to be formed by a suitable pattern positionedagainst the side of the tube 11 during the molding of the sand. A sheetgate or wide channel 35 is indicated for conducting the inolten iron tothe lowerpart of the casting recess 34, and a pouring spout 36 isarranged to connect with the gate. The'sand in the cope 33 may besupported and held by gaggers 37 or other devices known to the moldingart. For reasons that will appear it is preferable to arrange an exit orriser 38 for the molten iron, so that it can be poured into the mold inexcess and run out through the riser and thence overflow through agutter 39. The molten metal will be able to fill the casting space 34 tothe highest point thereof due to the porosity .of the sand, and theriser 38 preferably takes off from the recess 34 at a point as close aspossible to the upper side of the preformed tube 11. In some cases apermanent mold might be used in lieu of the sand mold described.

The arrangement thus described may be employed for casting a singleextension section 13 upon the steel tube, or by the arrangement shown inFig. 5 may be employed for simultaneous formation of a number of suchsections. The order of production of extension sections may be varied.Thus alternate sections maybe cast upon the tube and subsequently othersbetween them; or a series of sections may be cast and after the castingis cooled the tube may be shifted along for the production of anotherseries and so on until the full desired number of sections is cast. InFig. 5 the pouring spout 36 is shown as having multiple or dividedchannels 41 enterin the respective sheet gates 35 for the severasections; and likewise the several risers 38 are shown deliveringthrough separate overflow channels 42 to a common overflow point. Theseveral casting recesses 34 may be originally formed as a single recessand spaced before casting by a series of baked cores 43 arranged betweenthe successive sections and representing the spaces 23 shown in Fig. 2.

According to the present method the preformed tube is preferablypreheated to a fairly high degree for example 800 to 900 F. so as tosoften the metal or prepare'it for the fuse Welding operation by whichthe facing extensions are rendered integral with the tube. For thepurpose of such preheating a burner or torch 45 is indicated and thismay be used to drive through the tube flames from the combustion of oilor gas. Uniformity of preheating is desirable and I have devised anarrangement for electrically preheating the tube for this purpose. Whenthe blow torch is used it is preferably operated alternately from oneend and then the other end of the tube so as to bring the tubetemperature as high and as uniformly as possible over the entire lengthor portion to be treated.

The casting, it will be observed, is performed directly upon the surfaceof the preheated tube 11. The molten cast iron may be at a temperatureof about 2900 F. According to this invention the preferred operation isto allow the molten iron to fill the casting recess, and then while partof the iron flows out through the riser, keeping up a continuous flowthrough the gate 35, recess 34 and the riser 38, for a substantialperiod in order to elevate further the temperature of the steel tube,bringing it nearer to the fusion point and insuring integral uniting ofthe tube and extension, with molecular interlocking of the two portionsof the finished product.

The diagram, Fig. 4, indicates substantially the operation. The castingspace 34 is supposed to be full of molten iron. The sheet gate 35 bringsthe iron into the recess across the whole width thereof, while the sheetriser 38 is also of the full width, this arrangement insuring thecontinuous passage of a full width stream of molten iron through the re-7 stream to travel in more intimate contact with the tube asitprogresses and while it is cooling. j

The result is that the entire exposed and preheated surface of the tubeis. elevated to a fairly even temperature for integral uniting or fusewelding with the cast iron extension formed upon it. It is estimatedthat the tube steel, at its exposed surface, will in this process beraised nearly to, but not over 1250 to 1300 F., at which it will softenenough for welding or fusion" to the cast metal, without actuallymelting or running.

The referred manipulation is substantially as fo lows. The molten ironis poured from a ladle into the spout 36 first at a fast rate of flow inorder to fill the mold quickly. As soon as the mold is filled andoverflow at the riser commences, the pouring should be slowed down to asslow rate as practicable. By this plan the maximum heating up of thetube by the iron is secured with the minimum of erosion of the steel bythe stream of iron. The pouring ma be continued for about one minutemore, or ess. The extent of pouring is best determinedb the weight ofmetal and preferably severa times the weight of the casting itselfshould be flowed through the mold. For example, in casting four facingsections, as in Fi 5, and assuming that these will contain a out 25pounds of metal, a ladle may be employed which when filled to a certainpoint will hold 100 pounds of molten iron. The pouring will then becontinued until all of the iron from the ladle has passed into or fromthe mold.

The spout 36 being at a higher level than the discharge channel 39gravity will maintain the flow until the o eration is completed. Whenall of the iron 1s poured the casting will be allowed to cool and hardenand when subsequently removed from the mold will be found integrallyattached to the steel tube.

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The extent of the operation of flowing the hot iron along the steelsurface must be carefully determined. Excessive operation will causetheiron to wash away portions of the heated steel and so impair thestrength of the tube. lit the pouring is insufiiciently continued thesteel will not be brought to the welding temperature and there will beno real bond or effective fusion established between the metal of thetube and the extension. The result will be greatly impaired conductivityso that one of the main objects of the invention Would be effected; andmoreover the inadequately united portions are liable subsequently toseparate. The operation should be so calculated as to bring the steeltube to a welding temperature, the iron thereb becoming welded and fusedto the tube wit 1 a thorough union involving an intercrystallinestructure. The formation of bubbles at the line of union is precluded bythe described operation, since the bubbles tend to rise without havingaccess to the surface of the steel tube, as indicated at 48 in Fig. 4.

Many variations suggest themselves. Thus byza suitable elongated mold anentire twenty foot tube can be treated in one operation. The tube may beof any nature suitable to its purpose, and the facin or extension is notnecessarily of cast iron ut may be cast steel. The described molding andcasting method may be improved and quickened as follows. The moldportions containing the gates and risers may consist of previouslyprepared hard-baked dry sand cores, and the runner and pouring spout maylikewise be composed of'baked sand and locateddirectly on top of thebakedcore members. After the tube is placed in the mold the baked coresdefining the facing extension are placed against the tube, and thengreen sand is placed to surround the tube and cores and tamped tightly,before the pouring of the measured amount of molten iron as alreadydescribed. This system reduces errors and losses, and makes all castingsuniform; and accidental entry of dirt into the mold is prevented. Themolding time is shortened, and the molding requires less skill. Theoutput from each mold is increased, since one set of men may be employedin making the separate baked cores, While another set is applyingcoresand forming the molds. The larger output is therefore accompaniedby lower cost of pro-' duction. The small cores separating the castinginto longitudinal sections may advantageously be composed of cast iron,and they may be pasted and covered with sand before being applied at themold; this giving a cleaner separation between sections, and giving amore uniform result as the cast iron core is not subject to crushing;and it is readily knocked out after the cooling and removal of theproduct.

Features disclosed but not herein claimed are reserved for claim incopending application Serial No. 309,844, filed October 2, 1928.

There has thus been described a method of forming an extension upon atube embodying the principles and attaining the objects of the presentinvention. Various matters of method, operation, combination,arrangement and structure may be variously modified without departingfrom the principles and therefore it is not intended to limit theinvention to such matters except to the ex-- tent set forth in theappended claims.

What is claimed is:

1. Apparatus for applying at one exterior side of a preformed tube anintegral extension, comprising a mold adapted to receive a section ofthe preformed tube with its end or' ends projecting externally, and saidmold having mold material defining a casting space of the shape of theextension at one side of the tube while protecting the relld mainder ofthe tube, and having a gate for delivering molten metal into the lowerpart of the casting space, and an exit passage from the upper part ofthe space to an overflow point.

2. The method of forming upon one side of a preformed ferrous metalcirculation tube an integral heat-absorbing extension of ferrous metal,comprising supporting the tube in position in a. mold with its side thatis to receive the extension exposed in a casting space of the shape ofthe extension, and with the remainder of the circumference of the tubeprotected by the mold material, flowing molten ferrous metal into andthrough the casting space in excess quantity, continuing such flowinguntil the tube metal attains welding temperature at its exposedcircumference, then stopping such flowing before melting of the tubemetal or substantial interflowing of metals, and allowing the extensionmetal to solidify under confinement to the shape of the extension;whereby integral union is effected of the similar metals of thepreformed tube and-the produced extension.

3. The method of forming upon one side only of a preformed metalliccirculation tube an integral heat-absorbing extension of similar metal,comprising supporting the tube in position in a mold with its side thatis to receive the extension exposed in a casting space of the shape ofthe extension, and with the remainder of the circumference of the tubeprotected by the mold material, applying heat internally to the tube toheat the walls thereof both at the side exposed in the casting and atthe opposite side, flowing molten extension metal into and through thecasting space in excess quantity, continuing such flowing until the tubemetal attains welding temperature, then stopping such flowing beforemelting of the tube metal or substantial interflowing of metals, andallowing the extension metal to solidify under confinement to the shapeof the extension.

4. The method of forming upon one side of a preformed wrought steelcirculation tube an integral heat-absorbing extension of cast iron,comprising supporting the preformed tube in substantially horizontalposition in a mold with its side that is to receive the extensionexposed laterally in a casting space of the shape of the extension, andwith the remainder of the circumference of the tube protected by themold material, flowing molten cast iron continuously into and throughthe casting space in excess quantity, continuing such flowing until thetube steel attains welding temperature, then stopping such flowingbefore melting of the tube steel or injurious erosion thereof, andallowing the extension metal to solidify under confinement to the shapeof the extension.

5. The method as in claim 4. and wherein between a quarter and a half ofthe circumference of the preformed tube is exposed in the casting space,and the molten iron is admitted to a low part of the space so as to flowupwardly and to overflow from a higher point proximate to the surface ofthe tube.

6. Apparatus for applying along one side of a preformed tube a series ofintegral extensions, comprising a mold adapted to receive horizontallythe preformed tube and defining a series of casting spaces of the shapeof the extensions at one side of the tube, with separating cores betweenthe spaces, and gates for delivering molten metal into the lower part ofeach casting space, and exit passages from the upper part of each spaceto an overflow point.

7. Apparatus for applying at one side of a preformed tube an integralextension, comprising a two part mold adapted to receive the preformedtube horizontally between the mold parts and defining a casting space ofthe shape of the extension at one side of the tube, and having a gatedelivering into the lower part of the casting space at a point distantfrom the tube, and an exit passage leading from a point closely adjacentto the tube in the upper part of the space.

In testimony whereof, this specification has.

been duly signed.

ARTHUR T. HUNTER.

